Calculate the size of the local catchment area (contributing area), accumulated material, and flow path length, using top-down processing algorithms from the highest to the lowest cell. Top-Down Processing is new with SAGA GIS 2.1.3. See rsaga.parallel.processing() with older versions.
rsaga.topdown.processing(in.dem, in.sinkroute, in.weight, in.mean, in.material,
in.target, in.lin.val, in.lin.dir, out.carea, out.mean, out.tot.mat,
out.acc.left, out.acc.right, out.flowpath, step, method = "mfd",
linear.threshold = Inf, convergence = 1.1, env = rsaga.env(), ...)input: digital elevation model (DEM) as SAGA grid file (default file extension: .sgrd)
optional input: SAGA grid with sink routes
optional input: SAGA grid with weights
optional input: SAGA grid for mean over catchment calculation
optional input: SAGA grid with material
optional input: SAGA grid of accumulation target
optional input: SAGA grid providing values to be compared with linear flow threshold instead of catchment area
optional input: SAGA grid to be used for linear flow routing, if the value is a valid direction (0-7 = N, NE, E, SE, S, SW, W, NW)
output: catchment area grid
optional output: mean over catchment grid
optional output: total accumulated material grid
optional output: accumulated material from left side grid
optional output: accumulated material from right side grid
optional output: flow path length grid
integer >=1: step parameter
character or numeric: choice of processing algorithm (default "mfd", or 4):
0 Deterministic 8 ("d8" or 0)
1 Rho 8 ("rho8", or 1)
2 Braunschweiger Reliefmodell ("braunschweig" or 2)
3 Deterministic Infinity ("dinf" or 3)
4 Multiple Flow Direction ("mfd" or 4)
5 Multiple Triangular Flow Direction ("mtfd", or 5)
6 Multiple Maximum Gradient Based Flow Direction ("mdg", or 6)
numeric (number of grid cells): threshold above which linear flow (i.e. the Deterministic 8 algorithm) will be used; linear flow is disabled for linear.threshold=Inf (the default)
numeric >=0: a parameter for tuning convergent/ divergent flow; default value of 1.1 gives realistic results and should not be changed
list, setting up a SAGA geoprocessing environment as created by rsaga.env()
further arguments to rsaga.geoprocessor()
The type of object returned depends on the intern argument passed to the rsaga.geoprocessor(). For intern=FALSE it is a numerical error code (0: success), or otherwise (the default) a character vector with the module's console output.
Refer to the references for details on the available algorithms.
Deterministic 8:
O'Callaghan, J.F., Mark, D.M. (1984): The extraction of drainage networks from digital elevation data. Computer Vision, Graphics and Image Processing, 28: 323-344.
Rho 8:
Fairfield, J., Leymarie, P. (1991): Drainage networks from grid digital elevation models. Water Resources Research, 27: 709-717.
Braunschweiger Reliefmodell:
Bauer, J., Rohdenburg, H., Bork, H.-R. (1985): Ein Digitales Reliefmodell als Vorraussetzung fuer ein deterministisches Modell der Wasser- und Stoff-Fluesse. Landschaftsgenese und Landschaftsoekologie, H. 10, Parameteraufbereitung fuer deterministische Gebiets-Wassermodelle, Grundlagenarbeiten zu Analyse von Agrar-Oekosystemen, eds.: Bork, H.-R., Rohdenburg, H., p. 1-15.
Deterministic Infinity:
Tarboton, D.G. (1997): A new method for the determination of flow directions and upslope areas in grid digital elevation models. Water Ressources Research, 33(2): 309-319.
Multiple Flow Direction:
Freeman, G.T. (1991): Calculating catchment area with divergent flow based on a regular grid. Computers and Geosciences, 17: 413-22.
Quinn, P.F., Beven, K.J., Chevallier, P., Planchon, O. (1991): The prediction of hillslope flow paths for distributed hydrological modelling using digital terrain models. Hydrological Processes, 5: 59-79.
Multiple Triangular Flow Direction:
Seibert, J., McGlynn, B. (2007): A new triangular multiple flow direction algorithm for computing upslope areas from gridded digital elevation models. Water Ressources Research, 43, W04501.
Multiple Flow Direction Based on Maximum Downslope Gradient:
Qin, C.Z., Zhu, A-X., Pei, T., Li, B.L., Scholten, T., Zhou, C.H. (2011): An approach to computing topographic wetness index based on maximum downslope gradient. Precision Agriculture, 12(1): 32-43.
rsaga.parallel.processing(), rsaga.wetness.index(), rsaga.geoprocessor(), rsaga.env()
# NOT RUN {
# Calculation of contributing area with default settings:
rsaga.topdown.processing(in.dem = "dem", out.carea = "carea")
# Calculation of contributing area by maximunm downslope gradient:
rsaga.topdown.processing(in.dem = "dem", out.carea = "carea",
method = "mdg")
# }
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